The present invention relates to an image forming apparatus which is applied as, for example, an electrophotographic reproducing machine and where a drive and control system of a photosensitive drum and a transferring belt is improved. This Invention also relates to an image forming method using the image forming apparatus.
In an image forming apparatus such as an electrophotographic reproducing machine or the like, there is one where a photosensitive body drum is rotatably provided as an image supporting body or member and a transferring belt serving as transferring means is rotatably provided in opposition to the photosensitive drum. At a time of image formation, a toner image is formed on the photosensitive drum and it is transferred to a paper or sheet fed to the transferring belt according to rotation of a paper or sheet feeding roller. The paper on which an image has been transferred is fed into a fusing or fixing roller pair so that the toner image is fused or fixed on the paper.
The above-mentioned photosensitive drum is rotationally driven by a drum driving motor and the transfer belt is rotationally driven by a belt driving motor. At a time of rotational drive of the drum driving motor and the belt driving motor, FG pulses are input into a CPU for motor control from the drum driving motor and the belt driving motor. Rotational speeds of the photosensitive drum and the transfer belt are controlled by the CPU on the basis of this FG pulse inputting. That is, the rotational speeds of the photosensitive drum and the transfer belt are controlled such that their surfaces become the same constant speed.
The photosensitive drum is connected to the drum driving motor via a power transmission system comprising a drum shaft, a coupling, gears and the like. The transfer belt is spanned between a driving roller and a following or idle roller, and the belt driving motor is connected to the driving roller via a power transmission system comprising a roller shaft, a coupling, gears and the like.
In these circumstances, in a case that a problem regarding driving force transmission occurs in the above-mentioned power transmission system, even when the drum driving motor and the belt driving motor are normally rotated, the photosensitive drum and the transfer belt are not rotated normally in some cases.
In a case that the FG pulses transmitted from the drum driving motor and the belt driving motor are within a predetermined range, the CPU determines that, even when the photosensitive body drum or the transferring belt is not being rotated actually, it is being rotated normally. For this reason, there occurs a case that, for example, in a state where the transferring belt is not being rotated, the photosensitive drum, the sheet feeding roller and the fusing roller continue to rotate. In this case, friction occurs between the transferring belt and the photosensitive body drum, so that the transfer belt or the photosensitive drum is injured or a sheet is jammed in some cases.
Also, even in a case that both the photosensitive drum and the transferring belt are rotated, when a difference in rotating speed therebetween becomes 10% or more, friction occurs between the photosensitive drum and the transfer belt. Accordingly, there is a drawback that the photosensitive drum or the transfer belt may be injured or a sheet may be jammed like the above.
The present invention has been attained in view of the above circumstances, and an object thereof is to provide an image forming apparatus and an image forming method, where rotational drives of first driving means and second driving means are stopped on the basis of stopping of rotation of either one of an image supporting body or member and transferring means or on the basis of a difference equal to a predetermined value or more which occurs between the image supporting body and the transferring means, so that the image supporting body or the transferring means is prevented from being injured due to friction occurring between the image supporting body and the transferring means or conveyance jamming of a member or body on which an image is to be transferred is prevented from occurring.
A first aspect of the present invention comprises: image forming means for forming a latent image on an image supporting body; developing means for supplying developing agent to the latent image which has been formed by the image forming means; transferring means which contacts with the image supporting body to transfer the a developing agent image which has been developed by the developing means to a body on which an image is to be transferred; first driving means for rotationally driving the image supporting body; second driving means for rotationally driving the transferring means; first detecting means for detecting the rotating state of the image supporting body at a driving time of the first driving means; second detecting means for detecting the rotating state of the transferring means at a driving time of the second driving means; and controlling means for, when it is determined on the basis of detection signals sent from the first and second detecting means that one of the image supporting body and the transferring means has been stopped or that a difference in rotating speed between the image supporting body and the transferring means is a predetermined value or more, performing control so as to stop driving of the first and second driving means on the basis of this determination.
An image forming method of the present invention comprises: an image forming step for forming a latent image on an image supporting body; a developing step for developing the latent image which has been formed by the image forming step, by supplying developing agent to the latent image; a transferring step for transferring, by a transfer body contacting with the image supporting body, a developing agent image which has been developed by the developing step to a body on which an image is to be transferred; a driving step for rotationally driving the image supporting body by a first driving means and rotationally driving the transfer body by a second driving means; a detecting step for detecting the rotating states of the image supporting body and the transfer body; and a controlling step for determining whether or not the first and second driving means are normally rotating, when it is determined that they are normally rotating determining whether or not a difference in rotating speed between the image supporting body and the transfer body is a predetermined value or more on the basis of detection information detected in the detecting step, and, when the difference is a predetermined value or more, performing control so as to stop driving of the first and second driving means.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.